TERMINOLOGY Loading rack/loading platform = stair/platform operators use to get up to the tankcars. Gangway (aka drop downs, ramps, walkways, gantry's, bridges, platforms) = walk surface operator is using to get out to the tankcar dome. Crash box = railing on top of tankcar around dome. Gangway tracking = system that allows gangway to track along the length of the platform parallel to the tankcar (allows for mispotting of tankcar). Loading arm = flexible piping system operators are using to hook up to tankcar to load/unload.
CENTERLINE One of the biggest challenges we see is not allowing a large enough centerline. Greenfield versus retrofit. Single sided loading rack ~ the centerline is the distance from face of the loading rack/platform to the center of rail tracks. Double sided loading rack ~ the centerline is the distance from the center of one set of rail tracks to the other. Why it’s important/what it drives ~ staying out of rail envelope. Ideal centerline is 10’ ~ we can work with shorter/longer. Rule of thumb ~ 10’ plus the width of the platform (i.e. on single sided loading rack with 5’ wide platform a 15’ centerline is ideal, on a double sided loading rack with a 7’ wide platform 27’ is ideal). To long of a centerline can have an impact on the gangways (spring balance) and loading arms (reach).
TANGENT VERSUS CURVE Typically loading racks are built on a tangent/straight run of tracks (preferred). Can design for the curve/radius but there is a limit (12° is the max). Tracking gangways on a curve becomes difficult. Platform is built on a tangent/in straight sections with mitred corners. Curves increase cost. Usually requires additional gangways because the gangways then often have to track past a column which is difficult to do.
TANKCARS/SPOTTING Tankcar information/variances. Need to have good data on min/max lengths & heights of tankcars ~ longest car length plus # of spots drives overall platform length. Rail service provider doing the spotting versus spotting with own locomotive or trackmobile. Car spotting. 2 types, uncoupled and coupled. Uncoupled means breaking and spotting the tankcars cars at the gangway. Coupled means the tankcars are staying connected and the gangway has to pick up any mispotting. Drives gangway design ~ fix mounted gangway versus tracking gangway.
TYPE OF LOADING/ TYPE OF OPERATION Loading or unloading. Top loading/unloading versus bottom loading/unloading. Splash filling versus tight connection ~ aka atmospheric loading versus closed loop (recovering vapor). Loading with hoses versus loading arms. Has a relationship with gangway tracking.